Microwave Dielectric Properties of Ca0.8Sr0.2TiO3–Li0.5Sm0.5TiO3 Ceramics with Near-Zero Temperature Coefficient of Resonant Frequency

Abstract

The structural evolution and microwave dielectric properties of (1-x)Ca0.8Sr0.2TiO3–xLi0.5Sm0.5TiO3 (x=0–1.0) solid solutions were investigated. Most samples exhibit the single orthorhombic perovskite structure and a homogeneous microstructure with high density except for the composition with x=0.5 which included a small amount of the TiO2 phase. Increasing Li0.5Sm0.5TiO3 content results in a structural change in symmetry around x=0.8. A-site ordering structures were observed in compositions with x≥0.80. The dielectric constant (εr) decreased with increasing x. The quality factor (Q×f) decreased first up to x=0.5 with increasing x, then increased again up to x=0.82, and then decreased as x increased to x=1.0. The temperature coefficient of the resonant frequency (τf) decreased from high positive values to negative values with increasing x. A near zero τf was achieved at x=0.81. Optimized microwave dielectric properties were estimated to be εr=95, Q×f=3303 GHz, and τf=-1.8 ppm/°C at x=0.81.